Field emission displays (FEDs) are packaged vacuum microelectronic devices that are used in connection with computers, television sets, camcorder viewfinders, and other electronic devices requiring flat panel displays. FEDs have a baseplate and a faceplate juxtaposed to one another across a narrow vacuum gap. In large FEDs, a number of spacers are positioned between the baseplate and the faceplate to prevent atmospheric pressure from collapsing the plates together. The baseplate typically has a base substrate upon which a number of sharp, cone-shaped emitters are formed, an insulator layer positioned on the substrate having apertures through which the emitters extend, and an extraction grid formed on the insulator layer around the apertures. Some FEDs, and especially smaller FEDs, also have a backplate coupled to the faceplate such that the backplate encloses the baseplate in a vacuum space. The faceplate has a substantially transparent substrate, a transparent conductive layer disposed on the transparent substrate, and a photoluminescent material deposited on the transparent conductive layer. In operation, a potential is established across the extraction grid and the emitter tips to extricate electrons from the emitter tips. The electrons pass through the holes in the insulator layer and the extraction grid, and impinge upon the photoluminescent material in a desired pattern.
One problem with FEDs is that the internal components continuously outgas, which causes the performance of FEDs to degrade over time. The effects of outgassing are minimized by placing a as-absorbing material (commonly called getter material) within the sealed vacuum space. Accordingly, to absorb the gas in the vacuum chamber over an FED's lifetime, a sufficient amount of getter material must be incorporated into the FED before it is sealed. Also, a sufficient amount of space must be allowed between the getter material and the component parts of the FED to allow a passageway for the gas to travel to the surface area of the getter material.
In conventional FEDs, the getter material is deposited and activated on a metal plate separately from the other component parts of the FED. Getter material is activated by heating it to a temperature at which a passivation layer on its exposed surfaces is diffused. Non-evaporable getter materials used in FEDs activate at approximately 900.degree. C. The base substrate, transparent substrate and backplate, however, are generally made from materials that begin to deform at approximately 450.degree. C.-500.degree. C., the temperature range at which many glass substrates and semiconductor substrates anneal. Accordingly, in order to avoid damaging the substrates, unactivated getter material is conventionally deposited and then activated on a metal plate apart from the substrates. The metal plate with activated getter material is then mounted on one of the substrates of an FED. The metal plate and getter material together are generally about 150 .mu.m thick.
The metal plate and getter material are mounted on small FEDs differently than they are on large FEDs. In small FEDs, the metal plate is generally mounted on a support member between the backplate and the baseplate. In large FEDs, the metal plate is commonly mounted on either the faceplate, the baseplate, or in a pump out tube.
Conventional FEDs and manufacturing methods present unique problems for incorporating getter material into the display assemblies because the distance between the faceplate and baseplate should be minimized. One problem is that the thickness of the metal plate and getter material together is a limiting factor in reducing the distance between the faceplate and the baseplate. In large FEDs, the distance between the faceplate and the baseplate is desirably 25 .mu.m-200 .mu.m; the 150 .mu.m thickness of the getter material and metal plate, therefore, often requires the faceplate and baseplate to be spaced apart by more than the desired distance. Another problem is that the metal plate increases the cost to manufacture an FED because it is a separate part and must be securely attached to another component part of the FED to prevent it from coming loose. Loose metal plates are a significant problem in FEDs because small particles of getter material may break away from a loose plate, causing shorting to occur across the emitter tips.
In light of the problems associated with incorporating getter material on a metal plate into conventional FEDs, it would be desirable to develop an FED and a method of manufacturing an FED in which nonevaporable getter materials are securely attached to the FED in a minimal amount of space and are activated after being incorporated in the FED.